Connection of ceramic pin heating elements having exterior heating element shafts in a metal housing with simultaneous sealing from the combustion chamber is complex. The installation position causes contact between the heating element shafts having different polarity and the grounded housing. Therefore, to avoid short circuits, one of the two heating element shafts must be electrically insulated from the housing in the area of the seal seat. Also, the other heating element shaft, having opposite polarity, must be electrically insulated from the connector bolt. The application of electrical insulation layers is currently implemented through separate vitrification steps or through application, for example by printing, and burning-in of electrically insulating layers. To avoid one-sided mechanical stresses of the installed pin heating element due to the applied insulation layers, the corresponding open connector shaft is also provided with a layer of the same thickness but with electrical conductive properties, since there might otherwise be a danger of breakage of the ceramic pin heating element in the area of the seal seat. Another possibility is for the ceramic pin heating element to be fully insulated from the housing through application of a coating. As with a potential-free A-probe, contact is made through a divided terminal bolt.